This chapter briefly introduces international climate negotiations from the perspective of state environmental responsibility. In describing the evolution of the international norm of climate responsibility, with particular attention to China's contribution to that evolution, it addresses key events and tensions that have shaped the formation of climate responsibilities globally. China undoubtedly played a highly constructive role at the Paris Conference, and for the first time, China's head of state instead of its premier not only participated in international climate negotiations but also portrayed China as a determined facilitator of international climate agreement. In June 2017, Donald Trump indeed signed an executive order to withdraw the United States from the Paris Agreement, which political leaders and non-state actors worldwide harshly criticised. When the United States ratified the United Nations Framework Convention on Climate Change (UNFCCC) in 1992, it accepted common but differentiated responsibilities (CBDR), at least in principle.